Feedthrough assembly with feature for controlling component position

ABSTRACT

In some examples, a feedthrough assembly for a medical device may include a ferrule. The ferrule defines an aperture extending through the ferrule from an outer end surface defined by the ferrule to an end inner end surface defined by the ferrule. The aperture includes a first portion having a first diameter and a second portion having a second diameter less than the first diameter. The aperture defines a longitudinal axis extending therethrough and the ferrule defines a ledge between the first and second portions of the aperture that extends radially inward toward the longitudinal axis. The feedthrough assembly further may include a conductive pin within the aperture and an insulating member surrounding at least a portion of the pin. The insulating member may electrically insulate the conductive pin from the ferrule, and the ledge and a surface of the insulating member adjacent the ledge may define a space therebetween.

This application is a divisional filing of U.S. patent application Ser.No. 16/421,008, filed 23 May 2019, the entire contents of which isincorporated herein by reference.

TECHNICAL FIELD

This disclosure relates generally to medical devices and, moreparticularly, to electrical feedthroughs for medical devices.

BACKGROUND

Some types of medical devices, such as cardiac pacemakers or implantablecardiac defibrillator systems, may be used to provide cardiac sensingand therapy for a patient via one or more electrodes. Some medicaldevices include a feedthrough assembly that that provides an electricalpathway between an interior of a hermetically-sealed housing of themedical device to a point outside the housing. The feedthroughassemblies are generally insulated from the housing. Feedthroughassemblies in such devices may make electrical connections betweenelectrical circuitry within a housing of the medical device and leads,electrodes, or sensors external to the housing of the medical device.Some medical devices including a feedthrough assembly may be configuredto be implanted subcutaneously in a chest of the patient or within achamber of a heart of the patient, as examples. Some medical deviceshaving a pulse generator that is configured to be implanted outside ofthe heart may be electrically connected to one or more implantablemedical electrical leads that include one or more electrodes via afeedthrough assembly.

SUMMARY

In general, this disclosure is directed to feedthrough assemblies formedical devices and to techniques for manufacturing such feedthroughassemblies. Example feedthrough assemblies may include a ferrule thatdefines an aperture, an insulating member, and a conductive pin. Thetechniques may include assembling the feedthrough assembly and heatingthe insulating member such that the insulating member melts and flowsinto contact with the conductive pin.

As an example, a feedthrough assembly may include a ferrule, aconductive pin, and an insulating member configured to electricallyinsulate the conductive pin from the ferrule. The ferrule may define anouter end surface, an inner end surface, an aperture extending throughthe ferrule from the outer end surface to the inner end surface, and alongitudinal axis extending through the aperture from the outer endsurface to the inner end surface. The conductive pin and the insulatingmember may be positioned within the aperture with the insulating membersurrounding at least a portion of the conductive pin. The insulatingmember may be configured to support the conductive pin within theferrule, such as when the insulating member has been heated and flowedinto contact with the conductive pin.

The aperture may include a first portion extending from the outer endsurface to a point at least halfway from the outer end surface to theinner end surface and a second portion extending from the inner endsurface toward the point at least halfway from the outer end surface tothe inner end surface. The first portion of the aperture may have afirst diameter and the second portion of the aperture may have a seconddiameter that is less than the first diameter. The ferrule also maydefine a ledge between the first portion of the aperture and the secondportion of the aperture that extends radially inward toward thelongitudinal axis defined by the ferrule.

During a technique for manufacturing the feedthrough assembly, the ledgemay support the insulating member within the aperture at least prior toa portion of the technique that includes heating the insulating member.The insulting member may include a material configured to melt and flowwhen heated, such as glass. By providing support to the insulatingmember at least prior to heating the insulating member, the ledge mayhelp retain the insulating member within the aperture in a desiredposition prior to heating, which may help ensure that one or moreportions of the insulating member assume a desired position and/or shapeas the insulating member re-solidifies after heating.

Although the insulating member may be supported by the ledge at leastprior to heating the insulating member, at temperatures sufficient forthe insulating member to flow, the insulating member may be configuredto wet and lift from the ledge due to surface tension, such that theinsulating member at least partially fills the space between the pin andthe ferrule when the insulating member re-solifidies. The insulatingmember reach and, in some cases, exceed a temperature sufficient to flowduring heating, and may also remain above a threshold flow temperatureduring a portion of the time it cools. As the insulating member liftsfrom the ledge, the ledge and a surface of the insulating memberadjacent the ledge may define a space therebetween. The feedthroughassembly may further include an adhesive coated onto the surface of theinsulating member adjacent the ledge such that the adhesive fills atleast a portion of the space.

In some other examples, a feedthrough assembly configured for attachmentto a medical device may include a conductive pin and an insulatingmember. Such other examples may include a ferrule that does not define aledge or other feature configured to support the insulating member atleast prior to heating the insulating member. Instead, such techniquesmay utilize a support platform tool separate from the feedthroughassembly during the heating that includes a pedestal within a recess tosupport the insulating member.

Although such a pedestal may provide some support to a portion of theinsulating member (e.g., a portion closest to the conductive pin), thepedestal may not reliably control the position and/or shape that theinsulating member may assume as it re-solidifies during a method ofmanufacturing the feedthrough assembly. Thus, techniques formanufacturing such example feedthrough assemblies may result invariations in the shape and/or position of the insulating memberrelative to the conductive pin (i.e., where the insulating member is“pinned”). Such variations may affect the beam length of the conductivepin (i.e., the length of conductive pin extending above the insulatingmember toward an outer end surface of the ferrule). Issues associatedwith variations in the beam length of the conductive pin may occurduring implantation of an implantable medical device to which thefeedthrough assembly is attached if the beam undergoes applied loadconditions of a fixed displacement as opposed to a fixed load.Variations in the beam length of the conductive pin may be associatedwith undesirable variations in the one or more aspects of the mechanicalperformance of the conductive pin, such as in the cyclic fatigue of theconductive pin.

Additionally, the use of such pedestals to support an insulating memberduring manufacturing of a feedthrough assembly may cause defects inand/or contamination of one or more components of the feedthroughassembly. For example, as the insulating member lifts away from thepedestal during a method of manufacturing the feedthrough assembly, theinsulating member may break off of the pedestal. Additionally, theconductive pin may bend and/or be pulled out from the insulating memberas the insulating member re-solidifies if the position and/or shape ofthe insulating member is not controlled during manufacturing of thefeedthrough assembly.

Moreover, pedestals of such support platforms may be a source ofcontamination of the insulating member. Such pedestals may be formed ofgraphite, which may be less likely to stick to a glass insulating memberthan some other materials. However, graphite pedestals may depositgraphite on the insulating member as the feedthrough assembly is removedfrom the support platform. Graphite or other foreign materials that maybe transferred from a pedestal to an insulating member may causeelectrical faults with a corresponding feedthrough assembly. Thus,methods of manufacturing feedthrough assemblies that include the use ofsuch pedestals may result in undesirable variations, manufacturingdefects, and/or contamination. Moreover, testing may be needed to detectsuch variation, defects, and/or contamination in feedthrough assembliesmanufactured using such methods, thereby adding time and complexity tothe manufacturing process.

Example feedthrough assemblies described herein may include a ferruledefining an aperture and a ledge between first and second portions ofthe aperture that extends radially inward (e.g., from an inner wall ofthe ferrule that defines the aperture) toward a longitudinal axisdefined by the ferrule and that may support an insulating member withinthe aperture at least prior to heating of the insulating member. In someexamples, the ledge may help ensure that the insulating member assumes adesired shape and/or a desired position relative to the conductive pinafter the insulating member re-solidifies, which may reduce variationsin mechanical performance of the conductive pin that may occur withvariations in the beam length of the conductive pin, such as variationsin the cyclic fatigue of the conductive pin. Thus, the ledge mayeliminate reliance on graphite pedestals during the manufacturingprocess, thereby eliminating the need to test for manufacturing defectsand/or contamination caused by such pedestals. Moreover, in examples inwhich an adhesive is coated onto a lower surface of the insulatingmember, the ledge may enable formation of a better “lock” between theadhesive and one or more components of the feedthrough assembly,relative to other ferrules of other example feedthrough assemblies thatdo not define a ledge.

In one example, a feedthrough assembly for a medical device comprises aferrule configured for attachment to the medical device. The ferruledefines an outer end surface and an inner end surface, and an apertureextending through the ferrule from the outer end surface to the innerend surface. The aperture comprises a first portion extending from theouter end surface to a point at least halfway from the outer end surfaceto the inner end surface, the first portion having a first diameter, anda second portion extending from the inner end surface toward the pointat least halfway from the outer end surface to the inner end surface,the second portion having a second diameter that is less than the firstdiameter. The aperture defines a longitudinal axis extending through theaperture from the outer end surface to the inner end surface, and aledge between the first portion of the aperture and the second portionof the aperture, the ledge extending radially inward toward thelongitudinal axis. The feedthrough assembly further comprises aconductive pin within the aperture, and an insulating member within theaperture and surrounding at least a portion of the conductive pin,wherein the insulating member is configured to electrically insulate theconductive pin from the ferrule, and wherein the ledge and a surface ofthe insulating member adjacent the ledge define a space therebetween.

In another example, a method of manufacturing a feedthrough assembly fora medical device comprises receiving at least a portion of a ferruleconfigured for attachment to the medical device within a recess definedby a support platform and dimensioned to receive at least the portion ofthe ferrule. The ferrule defines an outer end surface and an inner endsurface, and an aperture extending through the ferrule from the outerend surface to the inner end surface. The aperture comprises a firstportion extending from the outer end surface to a point at least halfwayfrom the outer end surface to the inner end surface, the first portionhaving a first diameter, and a second portion extending from the innerend surface toward the point at least halfway from the outer end surfaceto the inner end surface, the second portion having a second diameterthat is less than the first diameter. The aperture defines alongitudinal axis extending through the aperture from the outer endsurface to the inner end surface, and a ledge between the first portionof the aperture and the second portion of the aperture, the ledgeextending radially inward toward the longitudinal axis. The methodfurther comprises receiving a conductive pin within the aperture suchthat the conductive pin extends through the ferrule, and receiving aninsulating member configured to electrically insulate the conductive pinfrom the ferrule within the aperture and around the conductive pin suchthat at least a portion of the insulating member is positioned betweenthe ledge and the outer end surface of the ferrule. The method furthercomprises heating the insulating member such that the insulating membermelts and flows into contact with the conductive pin, and discontinuingheating of the insulating member and allowing the insulating member tore-solidify. The insulating member is configured lift from the ledgesuch that the ledge and a surface of the insulating member adjacent theledge define a space therebetween.

In another example, an implantable medical device comprises a housing, aplurality of electrodes, and circuitry within the housing, the circuitryconfigured to at least one of sense electrical signals or deliverelectrical therapy via the electrodes. The implantable medical devicefurther comprises a feedthrough assembly comprising a ferrule configuredfor attachment to the medical device. The ferrule defines an outer endsurface and an inner end surface, and an aperture extending through theferrule from the outer end surface to the inner end surface. Theaperture comprises a first portion extending from the outer end surfaceto a point at least halfway from the outer end surface to the inner endsurface, the first portion having a first diameter, and a second portionextending from the inner end surface toward the point at least halfwayfrom the outer end surface to the inner end surface, the second portionhaving a second diameter that is less than the first diameter. Theaperture defines a longitudinal axis extending through the aperture fromthe outer end surface to the inner end surface, and a ledge between thefirst portion of the aperture and the second portion of the aperture,the ledge extending radially inward toward the longitudinal axis. Thefeedthrough assembly further comprises a conductive pin within theaperture, and an insulating member within the aperture and surroundingat least a portion of the conductive pin, wherein the insulating memberis configured to electrically insulate the conductive pin from theferrule, and wherein the ledge and a surface of the insulating memberadjacent the ledge define a space therebetween.

In another example, a feedthrough assembly comprises a ferrule definingan outer end surface and an inner end surface, and an aperture extendingthrough the ferrule from the outer end surface to the inner end surface.The aperture comprises a first portion extending from the outer endsurface to a point at least halfway from the outer end surface to theinner end surface, the first portion having a first diameter, and asecond portion extending from the inner end surface toward the point atleast halfway from the outer end surface to the inner end surface, thesecond portion having a second diameter that is less than the firstdiameter. The aperture defines a longitudinal axis extending through theaperture from the outer end surface to the inner end surface, and aledge between the first portion of the aperture and the second portionof the aperture, the ledge extending radially inward toward thelongitudinal axis. The feedthrough assembly further comprises conductivepin within the aperture, and an insulating member within the apertureand surrounding at least a portion of the conductive pin, wherein theinsulating member is configured to electrically insulate the conductivepin from the ferrule, and wherein the ledge and a surface of theinsulating member adjacent the ledge define a space therebetween.

This summary is intended to provide an overview of the subject matterdescribed in this disclosure. It is not intended to provide an exclusiveor exhaustive explanation of the apparatus and methods described indetail within the accompanying drawings and description below. Furtherdetails of one or more examples are set forth in the accompanyingdrawings and the description below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual drawing illustrating an example of a medicaldevice system including an implantable medical device that includes anexample feedthrough assembly, and an external device, in conjunctionwith a patient's heart;

FIG. 2 is a conceptual drawing illustrating an example of a leadlessimplantable medical device that includes another example feedthroughassembly;

FIG. 3 is a conceptual drawing illustrating a manufacturing device withexample feedthrough assemblies received within corresponding recessesdefined by a support platform of the manufacturing device;

FIG. 4 is a cross-sectional view of a multi-seal header structure thatmay be included in an example feedthrough assembly, where thecross-section is taken along a plane parallel to a longitudinal axis ofone of a plurality of apertures defined by a ferrule of the headerstructure and through the aperture;

FIG. 5 is a cross-sectional view of another example feedthrough assemblythat includes a ferrule defining a single aperture, where thecross-section is taken through the aperture and along a plane parallelto a longitudinal axis defined by the aperture, prior to melting aninsulating member of the feedthrough assembly during a method ofmanufacturing the feedthrough assembly;

FIG. 6 is a cross-sectional view of another example feedthrough assemblythat includes the header structure of FIG. 4, where the cross-section istaken through an aperture of the plurality of apertures along a planeparallel to a longitudinal axis defined by the aperture;

FIG. 7 is a cross-sectional view of another example feedthrough assemblythat includes a ferrule defining two apertures, where the cross-sectionis taken through the apertures along a plane parallel to longitudinalaxes defined by the apertures;

FIG. 8 is a cross-sectional view of another example feedthrough assemblythat includes a ferrule that defines two apertures, where thecross-section is taken through the apertures along a plane parallel tolongitudinal axes defined by the apertures;

FIG. 9 is a functional block diagram illustrating an exampleconfiguration of the implantable medical device of FIG. 2; and

FIG. 10 is a flow diagram illustrating an example technique formanufacturing a feedthrough assembly.

DETAILED DESCRIPTION

In general, this disclosure describes example feedthrough assemblies formedical devices. Such feedthrough assemblies may include a ferrule, aconductive pin, and an insulating member configured to electricallyinsulate the conductive pin from the ferrule. In some examples, afeedthrough assembly may include a header structure configured forattachment to a medical device. The header structure may include aferrule defining one or more apertures, each aperture of which may beassociated with a corresponding electrical connection between differentcomponents of a medical device. Although the example feedthroughassemblies are generally described herein as being configured forattachment to a medical device, it should be understood that any of theexample feedthrough assemblies described herein alternatively may beconfigured for attachment to a non-medical device.

The ferrule may define an outer end surface, an inner end surface, atleast one aperture, and a longitudinal axis extending through theaperture from the outer end surface to the inner end surface. In someexamples, the aperture may define a first portion having a firstdiameter and extending from the outer end surface to a point at leasthalfway from the outer end surface to the inner end surface. Theaperture also may define a second portion that extends from the innerend surface toward the point at least halfway from the outer end surfaceto the inner end surface and that has a second diameter that is lessthan the first diameter. In any such examples, the conductive pin andthe insulating member of the feedthrough assembly may be positionedwithin the aperture such that the insulating member surrounds at least aportion of the conductive pin.

In some examples, the ferrule further may define a ledge between thefirst portion of the aperture and the second portion of the aperturethat extends radially inward toward the longitudinal axis defined by theferrule. For example, the ledge may define a surface in a planesubstantially orthogonal to the longitudinal axis. In other examples,the ledge may define a third portion of the aperture that extendsbetween the first portion and the second portion such that a diameter ofthe third portion tapers from the first diameter at a junction of thethird portion and the first portion to the second diameter at a junctionof the third portion and the second portion. In still other examples,the ferrule may define an aperture that tapers in diameter from an upperdiameter at the outer end surface of the ferrule to a lower diameter atthe inner end surface of the ferrule.

In some examples, the insulating member may comprise a material that isconfigured to melt and flow when heated, such as during a method ofmanufacturing the feedthrough assembly. In such examples, a ledgedefined by the ferrule may be configured to support the insulatingstructure at least prior to its reaching a temperature at which it maymelt and flow, which may help ensure that the insulating member assumesa desired shape and/or position after the insulating memberre-solidifies. For example, the ledge may help ensure that theconductive pin has a desired beam length in the finished feedthroughassembly. As the beam length of the conductive pin may have an effect onthe mechanical performance of the feedthrough assembly (e.g., fromeffects of variations in the cyclic fatigue of the conductive pin),controlling the beam length of the conductive pin may help ensureconsistent mechanical performance of the feedthrough assembly betweendifferent feedthrough assemblies of the same type. In this manner, theexample ledges described herein may help ensure desirable mechanicalperformance of the example feedthrough assemblies described herein.Moreover, such ledges may reduce or eliminate reliance on supportpedestals (e.g., a graphite pedestals) of support platforms used duringmethods of manufacturing such feedthrough assemblies.

In examples in which the ferrule defines a ledge, the ledge and asurface of the insulating member that is adjacent to the ledge maydefine a space therebetween. The insulating member may be a glassinsulating member, which may be configured to melt and flow into contactwith the conductive pin during a method of manufacturing the feedthroughassembly. In some such examples, the insulating member may be configuredto support the conductive pin within the ferrule at least after theinsulating member re-solidifies. In this manner, the insulating membermay provide mechanical integrity to the feedthrough assembly in additionto electrically insulating the conductive pin from the ferrule.

In some examples in which a ferrule defines a ledge, the insulatingmember may be configured to lift from the ledge while flowable and thenre-solidify during a method of manufacturing the feedthrough assembly toform a space between the ledge and the surface of the insulating memberthat is adjacent to the ledge (e.g., a lower surface of the insulatingmember). In some examples, the feedthrough assembly may further includean adhesive coated onto the surface of the insulating member adjacentthe ledge such that the adhesive fills at least a portion of the space.In such examples, the ledge may define additional surface area of theferrule to which the adhesive may adhere, relative to ferrules of otherexample feedthrough assemblies that do not define such a ledge.Moreover, a position of the surface of the ledge relative to a surfaceof the ferrule that defines a second portion of the aperture may helpcreate a “lock” between the adhesive and one or more of the insulatingmember, the conductive pin, or the ledge. In this manner, the ledge mayhelp improve adhesion between components of the feedthrough assembly andcontribute to the mechanical integrity of the feedthrough assembly.

FIGS. 1 and 2 illustrate example medical devices that may include one ormore of the example feedthrough assemblies described herein. The examplefeedthrough assemblies included in the medical devices of FIGS. 1 and 2may be configured to electrically connect a pulse generator to one ormore electrodes. Electrodes of the medical devices of FIGS. 1 and 2 maybe configured to deliver an electrical signal (e.g., therapy such ascardiac pacing) and/or configured to provide at least one sensingvector, in accordance with the examples described herein. It should benoted that medical devices that include one or more of the examplefeedthrough assemblies described herein may not be limited to treatmentof a human patient. In alternative examples, medical devices thatinclude one or more of the example feedthrough assemblies describedherein may be implemented in non-human patients, e.g., primates,canines, equines, pigs, ovines, bovines, and felines. These otheranimals may undergo clinical or research therapies that may benefit fromthe subject matter of this disclosure.

FIG. 1 is a conceptual drawing illustrating an example of medical devicesystem 2, including a leaded IMD 4A and an external device 8, inconjunction with heart 6 of a patient. Medical device system 2, whichincludes IMD 4A and external device 8, is an example of a medical devicesystem configured to deliver cardiac therapy to heart 6 of the patient.In some examples, IMD 4A may be an implanted, multi-channel cardiacpacemaker, implantable cardioverter-defibrillator (ICD), implantablepulse generator (IPG), extravascular pacemaker and/or ICD, or other IMDor combination of such IMDs configured to deliver cardiac therapy toheart 6. However, some of the components of the IMDs described herein,such as components of a feedthrough assembly, may be utilized with typesof external medical devices or other types of IMDs, such as other IMDsconfigured to deliver cardiac electrical therapy. Although system 2 isdescribed herein in the context of cardiac electrical therapy, one ormore aspects of system 2 (e.g., a configuration of a feedthroughassembly of IMD 4A) may be adapted to IMDs configured to deliver othertypes of electrical therapy to a patient, as well as to IMDs thatprovide physiological sensing and monitoring, but do not necessarilyprovide therapy.

In some examples, IMD 4A may be configured to sense electrical signalscorresponding to the depolarization and repolarization of heart 6, e.g.,a cardiac electrogram (EGM), via electrodes on one or more leads 12, 14,and 16 or the housing of IMD 4A. Additionally, or alternatively, IMD 4Amay sense electrical signals corresponding to the depolarization andrepolarization of heart 6 via extravascular electrodes (e.g., electrodespositioned outside the vasculature of the patient), such as epicardialelectrodes, external surface electrodes, subcutaneous electrodes, andthe like. In any such examples, the configurations of electrodes used byIMD 4A for sensing and pacing may be unipolar or bipolar. In someexamples, system 2 may determine heart rate to, e.g., detect arrhythmia,based on the electrical signals sensed via the electrodes. IMD 4A mayalso deliver therapy in the form of electrical signals to heart 6 viaelectrodes located on one or more leads 12, 14, and 16 or a housing ofIMD 4A. In the illustrated example, IMD 4A is connected to leads 12, 14and 16, and may be communicatively coupled to external device 8.

Leads 12, 14, and 16 extend into heart 6 of the patient to senseelectrical activity of heart 6 and to deliver electrical stimulation toheart 6. In the example shown in FIG. 1, RV lead 12 extends through oneor more veins (not shown), vena cava 20, RA 22, and into RV 24 forsensing right ventricular cardiac signals and delivering pacing orshocking pulses to RV 24. Right atrial lead 14 extends through one ormore veins and vena cava 20 and is positioned such that a distal end ofLV lead 16 is in the vicinity of RA 22 and vena cava 20 for sensingright atrial cardiac signals and delivering pacing or shocking pulses toRA 22. LV lead 16 extends through one or more veins, vena cava 20, RA22, and into coronary sinus 26 (illustrated in phantom) to a regionadjacent to the free wall of LV 28 of heart 6. In some examples,electrodes of lead 16 may be used in combination with electrodes of lead12 and/or lead 14 for delivering electrical shocks for cardioversion anddefibrillation therapies. In other examples, lead 16 may also beequipped with a distal tip electrode and ring electrode for pacing andsensing functions in the left chambers of heart 6.

In the illustrated example, lead 12 includes bipolar electrodes 32 and34, which may be located adjacent to a distal end of lead 12. Lead 14includes bipolar electrodes 36 and 37, which may be located adjacent toa distal end of lead 14. Lead 16 may be a multipolar LV lead and mayinclude electrodes 38 and 40, and electrodes 42, 44, 46, and 48. In someexamples, electrodes 42, 44, 46, and 48 may be located adjacent to adistal end of lead 16, as illustrated in FIG. 1. In some examples,electrodes 38, 40, 42, 44, 46, and/or 48 of lead 16 may be segmentedelectrodes having a plurality of discrete electrodes arranged atrespective circumferential positions around the circumference of lead16.

Electrodes 34 and/or 36 may be extendable helix tip electrodes and maybe mounted retractably within respective insulative electrode heads. Forexample, electrode 34 may be mounted retractably within insulativeelectrode head 45 positioned on lead 12 and electrode 36 may be mountedretractably within an insulative electrode head positioned on lead 14(not shown), respectively. In some examples, one or both of leads 12 and14 may also include one or more elongated coil electrodes, such as coilelectrode 30 of lead 12 and/or a coil electrode 49 of lead 14. In someexamples, electrodes 30-49 of leads 12, 14, and 16 may be electricallycoupled to a respective conductor within a lead body of a correspondingone of leads 12, 14, and 16, and thereby coupled to circuitry within IMD4A.

In some examples, leads 12, 14, and 16 respectively include in-lineconnectors 50, 52, and 54. IMD 4A may further include an IPG 56, whichmay include a connector block 58 and a hermetically-sealed housing 60.Connector block 58 may house a feedthrough assembly (not shown)configured to electrically connect leads 12, 14, and 16 with electroniccomponents included within housing 60 of IPG 56 via in-line connectors50, 52, and 54. In-line connectors 50, 52, and 54 may be configured tofit into corresponding bores of connector block 58, which may be coupledto corresponding conductive components of a feedthrough assembly of IPG56 (e.g., conductive pins), thereby connecting electrodes 30-49 of leads12, 14, and 16 to IPG 56. The feedthrough assembly of IPG 56 may includea different ferrule for each electrode on leads 12, 14, and 16, each ofwhich may define an aperture in which a conductive pin and an insulatingmember are received. Each of the conductive pins of the feedthroughassembly may be part of a different corresponding electrical connectionbetween IPG 56 and one of the electrical conductors of leads 12, 14, and16 via in-line connectors 50, 52, and 54. In some examples, thefeedthrough assembly of IPG 56 may include one or more features of theexample feedthrough assemblies illustrated in FIGS. 4-9, which mayconfer one or more advantages described below with respect to suchfeatures of the example feedthrough assemblies of FIGS. 4-9.

In some examples, one or more outward-facing portions of housing 60 maybe uninsulated, and thus may enable housing 60 to be used as a housingelectrode. In some examples, substantially all of housing 60 may beuninsulated, such that substantially all of housing 60 defines thehousing electrode. In some other examples, housing 60 may define one ormore additional housing electrodes (not shown), which may be defined bycorresponding divisions between insulated and uninsulated portions ofhousing 60.

In some examples, IMD 4A may be configured for sensing of electricalsignals corresponding to a cardiac electrogram of heart 6 via anycombination of electrodes 30-49 or via any one of electrodes 30-49 incombination with a housing electrode of housing 60. In any suchexamples, IMD 4A may be configured to deliver cardiac therapy to heart 6via any combination of electrodes 30-49. For example, IMD 4A may beconfigured to deliver at least one of fusion pacing or biventricularpacing to heart 6.

The configuration of medical device system 2 illustrated in FIG. 1 isone example configuration and is not intended to be limiting. Asdiscussed in further detail below with respect to FIG. 2, housing 60 mayenclose one or more accelerometers, therapy delivery circuitry, whichmay be configured to generate therapeutic stimulation, such as cardiacpacing, cardioversion, and defibrillation pulses, and sensing circuitryconfigured to sense electrical signals corresponding to a cardiacelectrogram signal of the patient and/or an activity level or activityof the patient. Housing 60 also may enclose and one or more of a memoryfor storing default and/or allowable values of one or more therapyparameters, diagnostics, feedback from the patient, and/or therapyprograms that may include values of one or more cardiac therapyparameters. Housing 60 further may enclose communication circuitryconfigured for communication between IMD 4A and external device 8 and/orother devices, such as an external device located with a clinician or aserver. Such components may enable IMD 4A to transmit data, such as datapertaining to a physiological condition of the patient and/or one ormore recommended values of one or more cardiac therapy parameters toexternal device 8.

FIG. 2 is a conceptual drawing illustrating an example configuration ofa leadless IMD 4B. As illustrated in FIG. 2, IMD 4B may include ahousing 70 and a cap 72. IMD 4B may be hermetically sealed to encloseand protect electrical components (e.g., processing circuitry, sensingcircuitry, therapy delivery circuitry, or other components) within IMD4B. In some examples, housing 70 and cap 72 may enclose some or all ofthe electrical components of IMD 4B. All or portions of housing 70and/or cap 72 may be electrically insulating.

In some examples, IMD 4B may include one or more electrodes, which maybe configured to deliver an electrical signal (e.g., therapy such ascardiac pacing) and/or configured to provide at least one sensingvector. For example, IMD 4B may include electrode 74, which may becarried on cap 72, and/or electrode 76, which may be a ring orcylindrical electrode carried on or formed by housing 70 of IMD 4B. Asillustrated in FIG. 2, electrode 76 may be disposed on an exteriorsurface of housing 70 and may be positioned to contact cardiac tissueupon implantation. In some examples, electrode 76 comprises more thanone electrode 76. In such examples, one electrode 76 may be used as acathode and another electrode may be used as an anode for deliveringcardiac pacing, such as bradycardia pacing, CRT, ATP, or post-shockpacing. In addition, one or more electrodes 76 may be used to detectintrinsic electrical signals from heart 6, such as an electrocardiogramsignal that processing circuitry enclosed within IMD 4B may receive viasensing circuitry enclosed within IMD 4B.

IMD 4B may include a feedthrough assembly (not shown) configured toelectrically connect electrode 74 with electronic components includedwithin housing 70 of IMD 4B. For example, a conductive pin of thefeedthrough assembly of IMD 4B may include a conductive pin thatelectrically connects electrode 74 to therapy delivery circuitry withinhousing 70 of IMD 4B. The feedthrough assembly of IMD 4B may include asingle ferrule, a single conductive pin, and a single insulating member.In some examples, the feedthrough assembly of IMD 4B may include one ormore features of the example feedthrough assemblies illustrated in FIGS.4-9, which may confer one or more advantages described below withrespect to such features of the example feedthrough assemblies of FIGS.4-9.

In some examples, a distal end of IMD 4B may include fixation mechanisms78, which may be configured to attach IMD 4B to patient tissue (e.g.,cardiac tissue) and retain electrode 74 in contact with cardiac tissue.Fixation mechanisms 78 may be active fixation tines, screws, clamps,adhesive members, or any other mechanisms for attaching a device totissue. In some examples, fixation mechanisms 78 may be constructed of amemory material, such as a shape memory alloy (e.g., nickel titanium),that retains a preformed shape. During implantation, fixation mechanisms78 may be flexed forward to engage tissue and allowed to flex backtowards housing 70, thereby embedding fixation mechanisms 78 in patienttissue.

IMD 4B also may include a manipulator attachment feature 80, which maybe positioned at a proximal end of IMD 4B. In some examples, manipulatorattachment feature 80 may be integral with housing 70. In otherexamples, manipulator attachment feature 80 may be a separate componentof IMD 4B that is attached to housing 70. In any such examples,manipulator attachment feature 80 may have a configuration that definesan opening 82, a hook shape, or any other suitable configuration thatmay enable tethering or extraction of IMD 4B to or from patient tissue.For example, manipulator attachment feature 80 may be configured toreceive or otherwise attach to a manipulator tool configured to enable aclinician to manipulate IMD 4B, such as during a procedure to implant orexplant IMD 4B. In some examples, manipulator attachment feature may beconfigured to attach IMD 4B to patient tissue. For example, a suture orother device may be inserted around and/or through manipulatorattachment feature 80 and attached to tissue. In this manner,manipulator attachment feature 80 may provide an attachment structure totether or retain IMD 4B within patient tissue at an implant site of IMD4B. Manipulator attachment feature 80 also may be used to extract IMD 4Bif IMD 4B is to be explanted (i.e., removed) from patient 4 if suchaction is deemed desirable.

In some examples, IMD 4B may include one or more leads orelectrode-bearing extensions configured to place one or more additionalelectrodes at another location within the patient, such as anotherlocation within a same chamber or a different chamber than a chamber ofthe patient's heart in which housing 70 may be implanted. In some suchexamples, housing 70 and cap 72 may carry fewer than all of theelectrodes used to perform functions described herein with respect toIMD 4B. In other examples, each electrode of IMD 4B may be carried byone or more leads (e.g., the housing of IMD 4B may not carry any of theelectrodes). In still other examples, IMD 4B or another pacing deviceused with one or more other devices, such as external device 8 of system2 of FIG. 1.

FIG. 3 is a conceptual drawing of a manufacturing device 90 with examplefeedthrough assemblies 92A-92C (collectively, “feedthrough assemblies92”) received within corresponding recesses 94 defined by a supportplatform 96 of the manufacturing device 90. In the example of FIG. 3,manufacturing device 90 is configured for the manufacture of feedthroughassemblies that each include two conductive pins, such as conductivepins 98A and 98B of feedthrough assembly 92A.

Support platform 96 defines recesses 94 in 60 groups of two, in whicheach group of two recesses 94 is spaced to receive the two conductivepins of a corresponding feedthrough assembly. Thus, in the example ofFIG. 3, support platform 96 is configured to hold up to sixty suchfeedthrough assemblies during one iteration of a method of manufacturingthe feedthrough assemblies. In other examples, however, manufacturingdevice 90 may be configured to hold more than sixty or fewer than sixtyfeedthrough assemblies that each include two conductive pins.Additionally, or alternatively, support platform 96 may define recesses94 in other configurations, such as singly or in groups of more thantwo. In any such examples, manufacturing device 90 may be configured foruse in the manufacture of feedthrough assemblies having any suitablenumber of conductive pins in any suitable arrangement.

Manufacturing device 90 may be formed of any suitable material capableof withstanding temperatures at least as high as those needed to melt aninsulating member of a feedthrough assembly without melting or otherwisedeforming. For example, one or more portions of manufacturing device 90may be formed of graphite or another material that would not stick tothe feedthrough assemblies 92, e.g., depending on the material(s) of thefeedthrough assemblies. In any such examples, manufacturing device 90does not include support pedestals positioned within recesses 94. Forexample, manufacturing device 90 does not include graphite pedestalsthat may deposit graphite residue on insulating members of feedthroughassemblies 92. Instead, one or more internal components of feedthroughassemblies 92 may be configured to provide support to insulating membersof feedthrough assemblies 92 during methods of manufacturing feedthroughassemblies 92 that include using manufacturing device 90. In thismanner, manufacturing device 90 may reduce or eliminate some of thedrawbacks associated with manufacturing devices that include suchsupport pedestals, such as by reducing or preventing contact betweengraphite of support platform 96 and insulating members of feedthroughassemblies 92.

FIGS. 4-8 are cross-sectional views of example feedthrough assemblies,and portions of example feedthrough assemblies, that are configured forattachment to suitable corresponding medical devices. FIGS. 4-7 arecross-sectional views of example feedthrough assemblies, and portions ofexample feedthrough assemblies, that each include a ferrule that definesat least one aperture and a ledge between first and second portions ofeach aperture of the at least one aperture defined by the ferrule. FIG.8 is a cross-sectional view of an example feedthrough assembly thatincludes a ferrule defining two apertures that each taper in diameterfrom an upper diameter to a lower diameter.

FIG. 4 is a cross-sectional view of a multi-seal header structure 100 ofthat may be included in an example feedthrough assembly, where thecross-section is taken along a plane parallel to a longitudinal axis 102of an aperture 106A of a plurality of apertures 106A-106G defined by aferrule 104 of header structure 100 and through aperture 106A. In someexamples, header structure 100 may be formed of titanium or anothersuitable metal. Header structure 100 may be 3D-printed, molded, ormanufactured according to any other suitable technique.

Header structure 100 may be configured for attachment to a particularmedical device, such as a medical device having one or more features ofIMD 4A. For example, the plurality of apertures 106A-106G defined byferrule 104 may enable a corresponding plurality of electricalconnections between a medical device to which header structure 100 maybe attached and a plurality of electrical leads. Header structure 100 isshown in FIG. 4 independently of other components of a feedthroughassembly in which header structure 100 may be included. During a methodof manufacturing a feedthrough assembly that includes header structure100, additional components may be positioned within the plurality ofapertures 106A-106G defined by ferrule 104 of header structure 100, asillustrated in FIG. 6 and described below with respect to FIG. 6.

Header structure 100 defines an outer end surface 108 and an inner endsurface 110 opposite outer end surface 108. A portion of outer endsurface 108 may be an outer end surface defined by ferrule 104 and aportion of inner end surface 110 may be an inner end surface defined byferrule 104. Outer end surface 108 may be more proximate to an outsideof a housing of a medical device to which header structure 100 may beattached (e.g., housing 60 of IMD 4A) and inner end surface 110 may bemore proximate to an inside of the housing of the medical device towhich header structure 100 may be attached. Apertures 106A-106G eachextend through ferrule 104 from outer end surface 108 to inner endsurface 110. In some examples, apertures 106A-106G may be drilled intoferrule 104 during a method of manufacturing header structure 100.

As illustrated in FIG. 4, an aperture 106A of apertures 106A-106Gincludes a first portion 112 and a second portion 114. First portion 112may extend from outer end surface 108 to a point 116 at least halfwayfrom outer end surface 108 to inner end surface 110. Second portion 114may extend from inner end surface 110 toward point 116. First portion112 may have a first diameter D₁, which may be from about 0.02 inches toabout 0.15 inches depending on the dimensions of other components of afeedthrough assembly that includes header structure 100 and the desiredelectrical performance of such a feedthrough assembly. Second portion114 may have a second diameter D₂ that is less than D₁. For example, D₁and D₂ may be selected to account for machining offsets. In some suchexamples, a common offset may be about ±0.002 inches for both aconductive pin and an insulating member that may be received withinaperture 106A, and a gap of about 0.001 inches may be allowed forassembly. Thus, in some examples, second diameter D₂ may be at leastabout 0.005 inches less than D₁ to account for the common offset for theconductive pin and the insulating member and the gap allowed forassembly.

In the example of FIG. 4, first portion 112 of aperture 106A extendsabout two-thirds of the way between outer end surface 108 and inner endsurface 110 to point 116, although this proportion may vary in otherexamples. In any such examples, point 116 may be located at leasthalfway from outer end surface 108 to the inner end surface, which mayenable an insulating member to be positioned within aperture 106A suchthat the insulating member does not extend past outer end surface 108.Although apertures 106A-106G are illustrated in the example of FIG. 4,ferrule 104 may define additional apertures or fewer apertures in otherexamples. In any such examples, one or more of apertures 106A-106G mayhave the same or different configurations as one or more others ofapertures 106A-106G. In addition, although only aperture 106A isdescribed below in detail for the sake of clarity, a configuration ofany of apertures 106B-106G may be substantially similar to theconfiguration of aperture 106A.

Ferrule 104 may further define a ledge 118 between first portion 112 ofaperture 106A and second portion 114 of aperture 106A. Ledge 118 mayextend radially inward into aperture 106A toward longitudinal axis 102defined by ferrule 104. In the example of FIG. 4, ledge 118 defines athird portion 120 of aperture 106A that extends between first portion112 and second portion 114. Ledge 118 may provide support for aninsulating member received within aperture 106A during a method ofmanufacturing a feedthrough assembly that includes header structure 100at least prior to heating and melting of the insulating member. In someexamples, the support provided by ledge 118 to an insulating member mayhelp control a position and/or shape that one or more portions of theinsulating member assumes after the insulating member re-solidifiesduring a method of manufacturing a feedthrough assembly that includesheader structure 100 (e.g., subsequent to heating and melting of theinsulating member). Additionally, or alternatively, ledge 118 may definea surface onto which adhesive applied to a lower surface of aninsulating member may adhere. One or more advantages that ledge 118 mayprovide to a feedthrough assembly that includes header structure 100 arefurther discussed below with respect to FIG. 6.

A diameter of third portion 120 tapers from D₁ at a junction of thethird portion and the first portion to D₂ at a junction of third portion120 and second portion 114. In some examples, a portion of ferrule 104that defines third portion 120 of aperture 106A may form an angle with aportion of ferrule 104 that defines first portion 112 of aperture 106Athat corresponds to an angle of a drill bit used to drill apertures106A-106G, such as a standard 60° drill bit angle. In such examples, thetapered diameter of third portion 120 may correspond to a tapereddimension of a drill bit used to drill aperture 106A and facilitatemachining of aperture 106A during a method of manufacturing headerstructure 100.

The tapered diameter of third portion 120 that corresponds to a tapereddimension of a drill bit used to drill aperture 106A may render aperture106A easier and/or less costly to manufacture than ledges having otherconfigurations. In some examples, drilling to form aperture 106A mayinclude at least two steps. For example, a first drill bit having alarger diameter may be followed with a second drill bit having a smallerdiameter and an angled tip. Using a second smaller diameter bit tocomplete aperture 106A may avoid vertical scratches in ferrule 104 that,if deep enough, may create a leak paths through the seal formed by theinsulating member. However, in other examples, a ledge defined by any ofthe example ferrules described herein may define a surface in a planesubstantially orthogonal to a longitudinal axis defined by an exampleferrule, such as illustrated in FIGS. 5 and 7 and described below withrespect to FIGS. 5 and 7.

In any such examples, header structure 100 may define one or morefeatures that may be configured to facilitate attachment of headerstructure 100 to a medical device. For example, outer end surface 108 ofheader structure 100 may define ledges 122A and 122B. Ledges 122A, 122Bmay be configured to integrate with one or more portions of a medicaldevice to which a feedthrough assembly that includes header structure100 may be attached. For example, ledges 122A, 122B may be configured tointegrate with a device shield such as a metal “can” of a medicaldevice. In some examples, a metal can of such a medical device may havea thickness of about 0.01 inches to about 0.02 inches. One or moreportions of such a metal can may be configured to be positioned over oneor more of ledges 122A, 122B. In some examples, ledges 122A, 122B mayhelp facilitate welding (e.g., laser welding) of header assembly 100 toa metal can of a medical device.

FIG. 5 is a cross-sectional view of another example feedthrough assembly130 that includes a ferrule 132 that defines a single aperture 134 and aledge 136, where the cross-section is taken through aperture 134 andalong a plane parallel to a longitudinal axis 138 defined by aperture134. FIG. 5 illustrates feedthrough assembly 130 during a method ofmanufacturing feedthrough assembly 130 and prior to steps of heating,melting, and re-solidifying one or more components of feedthroughassembly 130 during such a method.

Ferrule 132 may be formed of titanium or another suitable metal, such asby 3D-printing, molding, or any other suitable manufacturing technique.Ferrule 132 may be configured for attachment to a particular medicaldevice, such as a medical device having one or more features of IMD 4B.For example, ferrule 132 may enable a corresponding electricalconnection between a leadless medical device to which feedthroughassembly 130 may be attached and an electrode positioned on an exteriorof the medical device, such as electrode 74 of IMD 4B. One or morefeatures of ferrule 132 may be substantially similar to one or morecorresponding features of ferrule 104 of FIG. 4. For example, ferrule132 may define an outer end surface 140 and an inner end surface 142,and an aperture 134. Outer end surface 140 may be more proximate to anoutside of a housing of a medical device to which ferrule 132 may beattached (e.g., housing 70 of IMD 4B) and inner end surface 142 may bemore proximate to an inside of the housing of the medical device towhich ferrule 132 may be attached. Aperture 134 may extend throughferrule 132 from outer end surface 140 to inner end surface 142, and mayinclude a first portion 144 and a second portion 146. First portion 144may extend from outer end surface 140 to a point 148 at least halfwayfrom outer end surface 140 to inner end surface 142. Second portion 146may extend from inner end surface 142 toward point 148. First portion144 may have a first diameter D₁, which may be from about 0.02 inches toabout 0.15 inches, depending on the dimensions of other components offeedthrough assembly 130 and the desired electrical performance offeedthrough assembly 130. Second portion 146 may have a second diameterD₂ that is less than D₁. For example, D₁ and D₂ may be selected toaccount for machining offsets, as discussed with respect to aperture106A of FIG. 4, such that second diameter D₂ may be at least about 0.005inches less than D₁ to account for the common offset for the conductivepin and the insulating member and the gap allowed for assembly.

In the example of FIG. 5, first portion 144 of aperture 134 extendsabout four-fifths of the way from outer end surface 140 to inner endsurface 142 to point 148, although this proportion may vary in otherexamples. In any such examples, point 148 may be located at leasthalfway from outer end surface 140 to inner end surface 142, which mayenable an insulating member 150 to be positioned within aperture 134such that insulating member 150 and does not extend past outer endsurface 140.

As illustrated in FIG. 5, insulating member 150 may be received withinaperture 134 such that insulating member 150 surrounds at least aportion of a conductive pin 152 that also is received within aperture134. Conductive pin 152 may be formed of a suitable conductive material,such as niobium, titanium, or alloys thereof. Conductive pin 152 may bedimensioned for use with a particular medical device. For example,conductive pin 152 may be dimensioned for use with IMD 4B. In suchexamples, conductive pin 152 may have a length of about 0.1 inches toabout 2 inches and a width of about 0.05 inches to about 0.1 inches,although conductive pin may have any suitable dimensions for use withIMD 4B. Insulating member 150 may be dimensioned to at least partiallysurround conductive pin 152 when conductive pin 152 is received withinaperture 134.

In some examples, insulating member 150 may be configured toelectrically insulate conductive pin 152 from ferrule 132. For example,insulating member 150 may be made of an insulating material that isconfigured to melt and flow when heated. In some examples, insulatingmember 150 may be made of a glass material and may be configured to meltand flow into contact with conductive pin 152 when heated during amethod of manufacturing feedthrough assembly 130. In any such examples,insulating member 150 may support conductive pin 152 within ferrule 132at least after insulating member 150 re-solidifies.

Glass material of insulating member 150 may have any suitablecomposition. For example, glass material of insulating member 150 maycomprise, by mole percentage, about 30% BO, about 30% to about 40% of amember selected from the group consisting of CaO, MgO, SrO andcombinations thereof, where the individual amounts of CaO and MgO eachdo not exceed about 20%. The composition further may comprise, by molepercentage about 5% LaO, about 10%, SiO, and about 15% Al₂O₃. Othersuitable compositions for a glass material of insulating member 150 aredescribed in U.S. Pat. No. 8,288,654 by Taylor et al., the entirecontent of which is incorporated herein by reference. Such glasscompositions may provide one or more benefits, such as a long-termdurability and/or a reduced propensity for tensile cracks relative toother glass compositions.

In the example of FIG. 5, ledge 136 is positioned between first portion144 of aperture 134 and second portion 146 of aperture 134 and mayextend radially inward into aperture 134 toward longitudinal axis 138defined by ferrule 132. As illustrated in FIG. 5, ledge 136 may providesupport for insulating member 150 during a method of manufacturingfeedthrough assembly 130 at least prior to heating and melting of theinsulating member.

The support provided by ledge 136 to insulating member 150 prior toheating and melting of insulating member 150 may help control a positionand/or shape that one or more portions of insulating member 150 assumesas the insulating member 150 re-solidifies during a method ofmanufacturing feedthrough assembly 130. For example, ledge 136 may helpcontrol the position and/or shape of an upper surface of the insulatingmember relative to conductive pin 152. Controlling the position and/orshape of insulating member 150 may provide one or more benefits. Forexample, the position of the upper surface of insulating member 150relative to conductive pin 152 (i.e., where insulating member 150 is“pinned”) affects the length of a portion of conductive pin 152 thatextends above the upper surface of insulating member 150. The length ofthe portion of the conductive pin 152 that extends above the uppersurface of insulating member 150 (i.e., the “beam length” of conductivepin 152), which may affect one or more aspects of the mechanicalperformance of conductive pin 152, such as the cyclic fatigue ofconductive pin 152.

Additionally, or alternatively, ledge 136 may define a surface ontowhich adhesive applied to a surface of insulating member 150 adjacentledge 136 may adhere. During steps of a method for manufacturingfeedthrough assembly subsequent to the illustrated example of FIG. 5,insulating member 150 may be heated, then lift from ledge 136 andre-solidify to define a space between ledge 136 and a surface ofinsulating member 150 that is adjacent to ledge 136. As discussed belowwith respect to the example feedthrough assembly of FIG. 6, an adhesivecoated onto the surface of an insulating member adjacent a ledge (e.g.,ledge 136) may adhere to a surface of the ledge that partially definessuch a space, which may create a “lock” between the adhesive and one ormore insulating member 150, conductive pin 152, or ledge 136.

In some examples, ledge 136 may differ from ledge 118 in that ledge 136may define a surface in a plane substantially orthogonal to longitudinalaxis 138. As illustrated in FIG. 5, ledge 136 may further define achamfered edge surface extending between the plane substantiallyorthogonal to longitudinal axis 138 that defines a third portion ofaperture 134 that tapers from diameter D₁ of first portion 144 ofaperture 134 to diameter D₂ of second portion 146 of aperture 134. Inother examples, ledge 136 may not define a chamfered edge surface, butinstead may have a configuration similar to the configuration of ledge118 illustrated in FIG. 4.

In any such examples, ferrule 132 may further include an upper portion156 that at least partially surrounds and extends from a perimeter ofouter end surface 140 of ferrule 132. Upper portion 156 of ferrule 132may be integral with outer end surface 140 or attached to outer endsurface 140, such as via welding. Upper portion 156 may be configured tohelp retain a portion of a medical device to which feedthrough assembly130 in a desired position relative to feedthrough assembly 130. Forexample, upper portion 156 may be configured to help retain cap 72and/or electrode 74 of IMD 4B in a desired position relative tofeedthrough assembly 130. In examples in which IMD 4B includes anelectrical lead or other examples in which feedthrough assembly 130 isconfigured to be electrically connect an electrical lead (e.g.,electrodes of an electrical lead) to a pulse generator of a medicaldevice, upper portion 156 may be configured to help retain the leadrelative to feedthrough assembly 130 In any such examples, upper portion156 of ferrule 132 may help maintain an electrical connection betweenone or more electrodes of a medical device and a pulse generator of themedical device via feedthrough assembly 130.

FIG. 6 is a cross-sectional view of another example feedthrough assembly160 that includes header structure 100 of FIG. 4, where thecross-section is taken through aperture 106A along a plane parallel tolongitudinal axis 102 defined by aperture 106A. FIG. 6 illustrates thecomponents of feedthrough assembly 160 subsequent to steps of heating,melting, and re-solidifying of a glass insulating member 162 that may beconducted during a method of manufacturing feedthrough assembly 160.Insulating member 162 may be received within aperture 106A such thatinsulating member surrounds at least a portion of a conductive pin 164received within aperture 106A.

In some examples, one or more features of insulating member 162 and/orconductive pin 164 may be substantially similar to one or morecorresponding features of insulating member 150 and/or conductive pin152 of feedthrough assembly 130 of FIG. 5. For example, insulatingmember 162 may be a glass insulating member having a substantiallysimilar composition to insulating member 150. However, dimensions of oneor more features of insulating member 162 and/or conductive pin 164 maydiffer from corresponding dimensions of insulating member 150 and/orconductive pin 152. For example, insulating member 162 and/or conductivepin 164 may be dimensioned for use with IMD 4A instead of IMD 4B. Insuch examples, conductive pin 164 may have a length of about 0.1 inchesto about 2 inches and a width of about 0.05 inches to about 0.1 inches.Insulating member 162 may be dimensioned to at least partially surroundconductive pin 164 when conductive pin 164 is received within aperture106A.

In the example of FIG. 6, insulating member 162 has been melted, flowedinto contact with conductive pin 164 and allowed to re-solidify. In thismanner, insulating member 162 may support conductive pin within ferrule104 at least after insulating member 162 re-solidifies. As illustratedin FIG. 6, insulating member 162 may define an upper surface 166 and alower surface 168. In some examples, ledge 118 may support insulatingmember 162 in a desired position within aperture 106A at least prior toheating of insulating member 162. One or more other factors, such asdimensions and/or composition of insulating member 162, may affect anextent to which insulating member 162 flows upon melting. Although suchother factors may influence the position and/or shape that upper surface166 and/or lower surface 168 may assume, such factors may becontrollable during manufacturing of insulating member 162. However, thepositioning of insulating member 162 prior to heating and melting ofinsulating member 162 also may influence the position and/or shape thatupper surface 166 and/or lower surface 168 may assume. Thus, the supportprovided to insulating member 162 by ledge 118 at least prior to heatingof insulating member 162 may help control the position and/or shape thatupper surface 166 and/or lower surface 168 may assume as insulatingmember 162 re-solidifies.

In some examples, the position of upper surface 166 of insulating member162 relative to conductive pin 164 (i.e., where insulating member 162 is“pinned”) affects the length of a portion of conductive pin 152 thatextends above upper surface 166 of insulating member 162. The length ofthe portion of the conductive pin 164 that extends above upper surface166 (i.e., the “beam length” of conductive pin 164) may affect themechanical performance of conductive pin 164, such as by affecting thecyclic fatigue of conductive pin 164. The influence that ledge 118 mayhave position and/or shape that upper surface 166 assumes as insulatingmember 162 re-solidifies may affect the beam length of conductive pin164. Thus, in some examples, the support provided by ledge 118 toinsulating member 162 may help ensure desirable mechanical performanceof feedthrough assembly 160.

Additionally, or alternatively, ledge 118 may enable manufacturing offeedthrough assembly 160 without relying on a pedestal (e.g., a graphitepedestal) of a support platform to provide support to insulating member162. As the use of such pedestals may be associated with breakage and/orcontamination with foreign materials of one or more components offeedthrough assembly 160, manufacturing feedthrough assembly 160 withoutrelying on such pedestals may reduce or eliminate such drawbacks. Inthis manner, ledge 118 may help enable consistent manufacturing offeedthrough assembly 160 to one or more desired specifications, and/ormay help improve the yield of methods of manufacturing feedthroughassembly 160.

In some examples, insulating member 162 may be configured lift fromledge 118 and re-solidify during a method of manufacturing feedthroughassembly 160 to form a space 169 between ledge 118 and lower surface 168of insulating member 168. For example, insulating member 162 may beconfigured to lift from ledge 118 about 0.05 millimeters (mm) to about2.0 mm as it re-solidifies. Feedthrough assembly 160 may further includean adhesive coated onto lower surface 168 of insulating member 162adjacent the ledge 118. In some such examples, the adhesive fills atleast a portion of space 169 and adheres to ledge 118 in addition toinsulating member 162 and conductive pin 164. In such examples, ledge118 may define surface space of ferrule 104 to which adhesive may adherein addition to a surface of ferrule 104 that defines second portion 114of aperture 106A. Moreover, a position of the surface of ledge 118relative to the surface of ferrule 104 that second portion 114 ofaperture 106A may help create a “lock” between the adhesive and ledge118. In this manner, ledge 118 may help improve adhesion betweencomponents of feedthrough assembly 160 and contribute to the mechanicalintegrity of feedthrough assembly 160.

FIG. 7 is a cross-sectional view of another example feedthrough assembly180 that includes a ferrule 182 defining apertures 184A and 184B, wherethe cross-section is taken through apertures 184A and 184B along a planeparallel to longitudinal axes 186A and 186B defined by apertures 184Aand 184B. Feedthrough assembly 180 may be configured for attachment to aparticular medical device, such as a medical device that includes twoelectrical leads. For example, ferrule 182 may enable two correspondingelectrical connections between a medical device to which feedthroughassembly 180 may be attached and two electrical leads via apertures184A, 184B.

Ferrule 182 may be part of a header structure 188, which defines anouter end surface 190 and an inner end surface 192. Outer end surface190 may be more proximate to an outside of a housing of a medical deviceto which header structure 188 may be attached and inner end surface 192may be more proximate to an inside of the housing of the medical deviceto which header structure 188 may be attached. Portions of outer endsurface 190 may be an outer end surface defined by ferrule 182 andportions of inner end surface 192 may be an inner end surface defined byferrule 182. One or more features of feedthrough assembly 180 may besubstantially similar to one or more corresponding features offeedthrough assembly 160 of FIG. 6 and thus will not be discussed indetail with respect to FIG. 7. For example, one or both of ferrule 182may be substantially similar to ferrule 104 of feedthrough assembly 160.

Apertures 184A, 184B may be substantially similar to aperture 106A offeedthrough assembly 160. For example, apertures 184A and 184B mayinclude first portions 194A, 194B and second portions 196A, 196B. As inaperture 106A, first portions 194A, 194B may have a first diameter andsecond portions 196A and 196B may have a second diameter that is greaterthan the first diameter.

Ferrule 182 respectively may define ledges 198A, 198B positioned betweenrespective ones of first portions 194A, 194B and second portions 196A,196B. Feedthrough assembly further may include insulating members 200A,200B received within respective ones of apertures 184A, 184B. One ormore features of insulating members 200A, 200B may be substantiallysimilar to one or more corresponding features of insulating member 162of feedthrough assembly 160. For example, insulating members 200A, 200Bmay be received within respective ones of apertures 184A, 184B such thatinsulating members 200A, 200 at least partially surround conductive pins202A, 202B that also are received within respective ones of apertures184A, 184B.

Feedthrough assembly 180 may differ from feedthrough assembly 160 inthat ledges 198A, 198B may define respective surfaces in a planesubstantially orthogonal to longitudinal axes 186A, 186B, instead ofdefining third portions of apertures 184A, 184B that taper in diameterfrom the first diameter to the second diameter.

Insulating members 200A, 200B define upper surfaces 204A, 204B and lowersurfaces 206A, 206B. In some examples, the positions and/or shapes ofupper surfaces 204A, 204B may be substantially similar to the positionand/or shape of upper surface 166 of insulating member 162 offeedthrough assembly 160. The positions and/or shapes of lower surfaces206A, 206B may be substantially similar to the position and/or shape oflower surface 168 of insulating member 162. For example, lower surfaces206A, 206B respectively may define spaces 207A and 207B between ledges198A, 198B and respective lower surfaces 206A, 206B during a method ofmanufacturing feedthrough assembly 160 (e.g., after the temperature ofinsulating members 200A, 200B falls to a point where the insultingmembers no longer flow. Spaces 207A, 207B may be differently sizedand/or shaped than space 169 defined between lower surface 168 ofinsulating member 162 and ledge 118 due to the different configurationsof ledges 198A, 198B relative to ledge 118. Nonetheless, spaces 207A,207B defined between lower surfaces 206A, 206B and ledges 198A, 198B mayprovide one or more advantages similar to those described above withrespect to space 169 defined between lower surface 168 of insulatingmember 162 and ledge 118 of feedthrough assembly 160.

FIG. 8 is a cross-sectional view of another example feedthrough assembly210 that includes a ferrule 212 that defines two apertures 214A and214B, where the cross-section is taken through apertures 214A and 214Balong a plane parallel to longitudinal axes 216A and 216B defined byapertures 214A, 214B. Feedthrough assembly 210 may be substantiallysimilar to feedthrough assembly 180 illustrated in FIG. 7. Thus,features of feedthrough assembly 210 that corresponding to one or morefeatures of feedthrough assembly 180 will not be discussed in detailwith respect to FIG. 8. For example, feedthrough assembly 210 mayinclude a header structure 218 that includes ferrule 212 and defines anouter end surface 220 and an inner end surface 222. Outer end surface220 may be more proximate to an outside of a housing of a medical deviceto which header structure 218 may be attached and inner end surface 222may be more proximate to an inside of the housing of the medical deviceto which header structure 218 may be attached. Header structure 218 maybe substantially similar to header structure 188 of feedthrough assembly180.

Feedthrough assembly 210 may differ from feedthrough assembly 180 inthat the configurations of apertures 214A, 214B differ from theconfigurations of apertures 184A, 184B. For example, instead ofincluding a first portion having a first diameter and a second portionhaving a second diameter that is less than the first diameter, diametersof apertures 184A, 184B may taper from an upper diameter U_(D) nearouter end surface 218 to an inner diameter I_(D) near inner end surface220. In some examples, the taper between U_(D) and I_(D) may besubstantially continuous, as illustrated in FIG. 8. In any suchexamples, ferrule 212 may not define a ledges between first and secondportions of apertures 214A, 214B. Instead, the tapered diameters ofapertures 214A, 214B may provide one or more of the advantages describedabove with respect to example ferrules that define a ledge.

For example, the tapered diameters of apertures 214A, 214B also may helpretain insulating members 224A and 224B in a desired position withinapertures 214A, 214B at least prior to heating insulating members 224A,224B. In such examples, the insulating members 224A, 224B may have asubstantially continuous diameter prior to heating, similar toinsulating member 150 of feedthrough assembly 130 of FIG. 5. Thediameter of insulating members 224A, 224B prior to heating may besmaller than U_(D) and greater than I_(D). Thus, when insulating members224A, 224B are received within respective ones of apertures 214A, 214Bprior to heating, insulating members 224A, 224B may be supported withinapertures 214A, 214B in a position where the diameter of apertures 214A,214B is substantially similar to the diameter of insulating members224A, 224B. The support provided to insulating members 224A, 224B by thetapered diameters of apertures 214A, 214B at least prior to heating ofinsulating members 224A, 224B also may help position (e.g., relative torespective ones of conductive pins 228A, 228B) and/or shape that uppersurfaces 226A and 226B may assume as insulating members 224A, 224B flowand then re-solidify during a method of manufacturing feedthroughassembly 210.

Additionally, or alternatively, the tapered diameter of apertures 214A,214B may enable manufacturing of feedthrough assembly 210 withoutrelying on pedestals (e.g., graphite pedestals) of a support platform toprovide support to insulating members 224A, 224B. Thus, the tapereddiameters of apertures 214A, 214B may reduce or eliminate drawbacksassociated with such graphite pedestals as described above with respectto the example feedthrough assemblies of FIGS. 5-7.

FIG. 9 is a functional block diagram illustrating an exampleconfiguration of an IMD 4A. In some examples, one or more components ofIMD 4 may be substantially similar to one or more correspondingcomponents of any of IMD 4A of FIG. 1 or IMD 4B of FIG. 2. As shown inFIG. 9, IMD 4 includes processing circuitry 240, sensing circuitry 242,therapy delivery circuitry 244, sensors 246, communication circuitry248, and memory 250. In addition, IMD 4 includes one or more electrodes252, which may be any one or more electrodes of IMD 4A or one or moreelectrodes of IMD 4B. In some examples, memory 250 includescomputer-readable instructions that, when executed by processingcircuitry 240, cause IMD 4 and processing circuitry 240 to performvarious functions attributed to IMD 4 and processing circuitry 240herein. Memory 250 may include any volatile, non-volatile, magnetic,optical, or electrical media, such as a random access memory (RAM),read-only memory (ROM), non-volatile RAM (NVRAM), electrically-erasableprogrammable ROM (EEPROM), flash memory, or any other digital media.

Processing circuitry 240 may include fixed function circuitry and/orprogrammable processing circuitry. Processing circuitry 240 may includeany one or more of a microprocessor, a controller, a digital signalprocessor (DSP), an application specific integrated circuit (ASIC), afield-programmable gate array (FPGA), or equivalent discrete or analoglogic circuitry. In some examples, processing circuitry 240 may includemultiple components, such as any combination of one or moremicroprocessors, one or more controllers, one or more DSPs, one or moreASICs, or one or more FPGAs, as well as other discrete or integratedlogic circuitry. The functions attributed to processing circuitry 240herein may be embodied as software, firmware, hardware or anycombination thereof.

In some examples, processing circuitry 240 may receive (e.g., fromexternal device 18), via communication circuitry 248, a respective valuefor each of a plurality of cardiac sensing parameters, cardiac therapyparameters (e.g., cardiac pacing parameters), and/or electrode vectors.Processing circuitry 240 may store such parameters and/or electrodevectors in memory 250.

Therapy delivery circuitry 244 and sensing circuitry 242 areelectrically coupled to electrodes 252, which may include one or more ofelectrodes 252. Processing circuitry 240 is configured to controltherapy delivery circuitry 244 to generate and deliver electricalstimulation to heart 6 via electrodes 252. Electrical stimulation mayinclude, for example, pacing pulses, or any other suitable electricalstimulation. Processing circuitry 240 may control therapy deliverycircuitry 244 to deliver electrical stimulation therapy via electrodes252 according to one or more therapy programs including pacinginstructions that define a pacing rate, which may be stored in memory250.

In addition, processing circuitry 240 is configured to control sensingcircuitry 242 to monitor signals from electrodes 252 in order to monitorelectrical activity of a patient's heart. Sensing circuitry 242 mayinclude circuits that acquire electrical signals. Sensing circuitry 242may acquire electrical signals from a subset of electrodes 252.Electrical signals acquired by sensing circuitry 242 may includeintrinsic and/or paced cardiac electrical activity, such as atrialdepolarization and/or ventricular depolarization. Sensing circuitry 242may filter, amplify, and digitize the acquired electrical signals togenerate raw digital data. Processing circuitry 240 may receive thedigitized data generated by sensing circuitry 242. In some examples,processing circuitry 240 may perform various digital signal processingoperations on the raw data, such as digital filtering.

In some examples, in addition to sensing circuitry 242, IMD 4 optionallymay include sensors 246, which may comprise at least one of a variety ofdifferent sensors. For example, sensors 246 may comprise one or morepressure sensors and/or one or more accelerometers. Sensors 246 maydetect signals associated with one or more physiological parameters of apatient, such as an activity level, a hemodynamic pressure, and/or heartsounds. Processing circuitry 240 may use signal detected by sensors 246to adapt one or more cardiac pacing parameters, such as by increasing arate of delivery of pacing pulses in response to detecting an increasein the patient's activity level.

Communication circuitry 248 may include any suitable hardware (e.g., anantenna), firmware, software, or any combination thereof forcommunicating with another device, such as an external device (e.g., adevice configured for use in a home, ambulatory, clinic, or hospitalsetting to communicate with IMD 4 via wireless telemetry) or a patientmonitor. Under the control of processing circuitry 240, communicationcircuitry 248 may receive downlink telemetry from and send uplinktelemetry to other devices (e.g., external device 18) such as via anantenna included in communication circuitry 248.

FIG. 10 is a flow diagram illustrating an example technique formanufacturing a feedthrough assembly for a medical device. Although theexample technique of FIG. 10 is described in the context of feedthroughassembly 160 of FIG. 6, the example technique should not be understoodto be so limited, but instead may be applied to the manufacture of otherexample feedthrough assemblies within the scope of this disclosure.

The example technique of FIG. 10 includes receiving at least a portionof ferrule 104 within a recess defined by a support platform anddimensioned to receive at least the portion of ferrule 104 (260). Forexample, at least a portion of inner end surface 192 defined by ferrule104 may be received within the recess. In some examples, the supportplatform may be substantially similar to support platform 92 of FIG. 3and the recess may be substantially similar to a recess of recesses 94defined by support platform 92. Conductive pin 164 may be receivedwithin aperture 106A defined by ferrule 104 (262). For example,conductive pin 164 may be received within aperture 106A such thatconductive pin 164 extends through ferrule 104. In some such examples,conductive pin 164 may be positioned such that a portion of conductivepin 164 that extends from inner end surface 110 is supported by asurface of support platform 92 that defines a bottom interior portion ofthe recess of recesses 94. Receiving conductive pin 164 within aperture106A such that the portion of conductive pin 164 is supported by supportplatform 92 may help retain conductive pin 164 in a desired positionrelative to ferrule 104 during the example technique of FIG. 10.

Insulating member 162 may be received within aperture 106A and aroundconductive pin 164 such that at least a portion of insulating member 162is positioned between ledge 118 defined by ferrule 104 and a portion ofouter end surface 108 defined by ferrule 104 (264). For example,insulating member 162 may be received within aperture 106A such thatinsulating member 162 is supported by ledge 118 within aperture 106A.With conductive pin 164 and insulating member 162 so positioned,insulating member 162 may be heated such that insulating member 162melts and flows into contact with conductive pin 164 (266). As discussedwith respect to FIG. 6, insulating member 162 may be a glass insulatingmember. Thus, heating insulating member 162 may include heatinginsulating member 162 to a temperature sufficient to cause melting ofglass having the composition and configuration of insulating member 162.

After insulating member 162 melts and flows into contact with conductivepin 164 during heating of insulating member 162, the application of heatto insulating member 162 may be reduced or discontinued and insulatingmember 162 may be allowed to re-solidify. In some examples, insulatingmember 162 may be configured to support conductive pin 164 withinferrule 104 at least after insulating member 162 re-solidifies.Insulating member 162 may lift from ledge 118 when above a flowtemperature (e.g., due to surface tension of insulating member 162causing insulating member 162 to contract and lift) and re-solidify,such that ledge 118 and lower surface 168 of insulating member define aspace therebetween (268). For example, insulating member 162 may belifted from ledge 118 by about 0.05 mm to about 2.0 mm as insulatingmember 162 re-solidifies. In some examples, the space may help reduce apossibility of residual stress between ledge 118 and insulating member162. Moreover, as described below, the space defined by ledge 118 andlower surface 168 of insulating member 162 may enable better adhesionbetween an adhesive applied to lower surface 168 of insulating member162 and conductive pin 164 relative to other example feedthroughassemblies in which such a space is not defined.

In some examples, a method of manufacturing feedthrough assembly 160 mayfurther include removing feedthrough assembly 160 from support platform92 after allowing insulating member 162 to re-solidify. After removingfeedthrough assembly 160 from support platform 92, ferrule 104 may beattached to a medical device (e.g., IMD 4A of FIG. 1), such that a firstportion of conductive pin 164 extends from inner end surface 110 intohousing 60 of IMD 4A and a second portion of conductive pin 164 extendsfrom outer end surface 108 outside of housing 60.

In some examples, after feedthrough assembly 160 is removed from supportplatform 92, a method of manufacturing feedthrough assembly 160 mayfurther include applying an adhesive to lower surface 168 of insulatingmember 162 adjacent ledge 118 such that the adhesive fills at least aportion of the space defined by ledge 118 and lower surface 168 ofinsulating member 162. In such examples, the adhesive may be in contactwith conductive pin 164 along a length of conductive pin 164 that isadjacent the portion of the space filled by the adhesive. Filling atleast a portion of the space defined by ledge 118 and lower surface 168of insulating member 162 with the adhesive may help secure the positionof conductive pin 164 relative to one or more other components offeedthrough assembly 160 (e.g., insulating member 162 and/or ferrule104). Securing the position of conductive pin 164 relative to such othercomponents of feedthrough assembly 160 in such a manner may provide oneor more advantages, such as contributing to the mechanical integrity offeedthrough assembly 160 and/or the integrity of the electrical couplingof the components of feedthrough assembly 160 to other components of amedical device to which feedthrough assembly may be attached.

Various aspects of the techniques may be implemented within one or moreprocessors, including one or more microprocessors, DSPs, ASICs, FPGAs,or any other equivalent integrated or discrete logic circuitry, as wellas any combinations of such components, embodied in programmers, such asphysician or patient programmers, electrical stimulators, or otherdevices. The term “processor” or “processing circuitry” may generallyrefer to any of the foregoing logic circuitry, alone or in combinationwith other logic circuitry or any other equivalent circuitry.

In one or more examples, the functions described in this disclosure maybe implemented in hardware, software, firmware, or any combinationthereof. If implemented in software, the functions may be stored on, asone or more instructions or code, a computer-readable medium andexecuted by a hardware-based processing unit. Computer-readable mediamay include computer-readable storage media forming a tangible,non-transitory medium. Instructions may be executed by one or moreprocessors, such as one or more DSPs, ASICs, FPGAs, general purposemicroprocessors, or other equivalent integrated or discrete logiccircuitry. Accordingly, the terms “processor” or “processing circuitry”as used herein may refer to one or more of any of the foregoingstructures or any other structure suitable for implementation of thetechniques described herein.

In addition, in some aspects, the functionality described herein may beprovided within dedicated hardware and/or software modules. Depiction ofdifferent features as modules or units is intended to highlightdifferent functional aspects and does not necessarily imply that suchmodules or units must be realized by separate hardware or softwarecomponents. Rather, functionality associated with one or more modules orunits may be performed by separate hardware or software components, orintegrated within common or separate hardware or software components.Also, the techniques could be fully implemented in one or more circuitsor logic elements. The techniques of this disclosure may be implementedin a wide variety of devices or apparatuses, including an IMD, anexternal programmer, a combination of an IMD and external programmer, anintegrated circuit (IC) or a set of ICs, and/or discrete electricalcircuitry, residing in an IMD and/or external programmer.

Various aspects of the disclosure have been described. These and otheraspects are within the scope of the following claims.

What is claimed is:
 1. A method of manufacturing a feedthrough assemblyfor a medical device, the method comprising: receiving at least aportion of a ferrule configured for attachment to the medical devicewithin a recess defined by a support platform and dimensioned to receiveat least the portion of the ferrule, the ferrule defining: an outer endsurface and an inner end surface; an aperture extending through theferrule from the outer end surface to the inner end surface, theaperture comprising: a first portion extending from the outer endsurface to a point at least halfway from the outer end surface to theinner end surface, the first portion having a first diameter; and asecond portion extending from the inner end surface toward the point atleast halfway from the outer end surface to the inner end surface, thesecond portion having a second diameter that is less than the firstdiameter, wherein the aperture defines a longitudinal axis extendingthrough the aperture from the outer end surface to the inner endsurface; and a ledge between the first portion of the aperture and thesecond portion of the aperture, the ledge extending radially inwardtoward the longitudinal axis, wherein the ledge defines a third portionof the aperture extending between the first portion and the secondportion, and wherein a diameter of the third portion tapers from thefirst diameter at a junction of the third portion and the first portionto the second diameter at a junction of the third portion and the secondportion receiving a conductive pin within the aperture such that theconductive pin extends through the ferrule; receiving an insulatingmember configured to electrically insulate the conductive pin from theferrule within the aperture and around at least a portion of theconductive pin such that at least a portion of the insulating member ispositioned between the ledge and the outer end surface of the ferrule;heating the insulating member such that the insulating member melts andflows into contact with the conductive pin; and discontinuing heating ofthe insulating member and allowing the insulating member to re-solidify,wherein the insulating member is configured lift from the ledge suchthat the ledge and a surface of the insulating member adjacent the ledgedefine a space therebetween.
 2. The method of claim 1, wherein theinsulating member is supported by the ledge within the aperture at leastprior to heating of the insulating member.
 3. The method of claim 1,wherein the insulating member is configured to support the conductivepin within the ferrule at least after the insulating memberre-solidifies.
 4. The method of claim 1, wherein the aperture comprisesa plurality of apertures, the feedthrough assembly, and wherein thefeedthrough assembly further comprises a header structure configured forattachment to the medical device and comprising the ferrule.
 5. Themethod of claim 1, wherein the insulating member comprises a glassinsulating member.
 6. The method of claim 1, further comprising applyingadhesive to the surface of the glass insulating member adjacent theledge such that the adhesive fills at least a portion of the space. 7.The method of claim 1, wherein receiving at least the portion of theferrule within the recess comprises receiving at least the inner endsurface of the ferrule within the recess.
 8. The method of claim 1,wherein the ledge defines a surface in a plane substantially orthogonalto the longitudinal axis.
 9. The method of claim 8, further comprising:removing the feedthrough assembly from the support platform afterallowing the insulating member to re-solidify; and attaching the ferruleto the medical device such that a first portion of the conductive pinextends from the inner end surface into a housing of the medical deviceand a second portion of the conductive pin extends from the outer endsurface outside of the housing.
 10. A method for making a medicaldevice, the medical device comprising a housing, the method comprising:forming in the housing a feedthrough assembly, the feedthrough assemblycomprising a ferrule configured for attachment to the medical device,the ferrule defining: an outer end surface and an inner end surface; anaperture extending through the ferrule from the outer end surface to theinner end surface, the aperture comprising: a first portion extendingfrom the outer end surface to a point at least halfway from the outerend surface to the inner end surface, the first portion having a firstdiameter; and a second portion extending from the inner end surfacetoward the point at least halfway from the outer end surface to theinner end surface, the second portion having a second diameter that isless than the first diameter, wherein the aperture defines alongitudinal axis extending through the aperture from the outer endsurface to the inner end surface; and a ledge between the first portionof the aperture and the second portion of the aperture, the ledgeextending radially inward toward the longitudinal axis, wherein theledge defines a third portion of the aperture extending between thefirst portion and the second portion, and wherein a diameter of thethird portion tapers from the first diameter at a junction of the thirdportion and the first portion to the second diameter at a junction ofthe third portion and the second portion; an insulating member withinthe aperture, wherein the insulating member is configured toelectrically insulate a conductive pin from the ferrule, and wherein theledge and a surface of the insulating member adjacent the ledge define aspace therebetween.
 11. The method of claim 10, comprising supportingthe insulating member on the ledge within the aperture at least prior toheating of the insulating member.
 12. The method of claim 10, furthercomprising coating an adhesive onto the surface of the insulating memberadjacent the ledge such that the adhesive fills at least a portion ofthe space.
 13. The method of claim 10, further comprising inserting aconductive pin in the ferrule, and heating the insulating member suchthat the insulating member melts and flows into contact with theconductive pin.
 14. The method of claim 11, further comprising insertinga conductive pin in the ferrule, and heating the insulating member suchthat the insulating member melts and flows into contact with theconductive pin.
 15. The method of claim 13, wherein the insulting membercomprises glass.